In a conventional type of box aimed at moisture proof or drip proof properties, for instance, an outdoor box for accommodating an electric panel therein or the like, an opening/closing section thereof is covered with a waterproof seal or at the portion that the cable goes inside of the box or from the box to the ouside is protected by a waterproof gland packing or the like. In the structure described above, outside air is let in according to breathing phenomenon due to a difference in temperature between inside and outside of the box, which causes dew condensation to occur in the box, so that the present inventor proposed a dehumidifying device in which a vent path is provided in an air tight box and partitioned into small chambers which were shielded thereby into a plurality of stages (Refer to Japanese Patent Laid-Open Publication No. 322060/1993).
However, in this dehumidifying device, a dehumidifying effect becomes unsteady, when a density in water-vapor gas inside thereof becomes once high, according to charged particles such as water-vapor gas entering the internal section thereof or according to more charged particles electrified by the side of the frame such as water-vapor gas inside the frame, or humidity in the side to be dehumidified of the box side is stabilized disadvantageously at a comparatively high level.
In many cases, the water-vapor gas or charged particles in the air contain mainly electrolytic particles like those contained in sea water, so that dusts together with these electrolytic particles cause a moisture-permeable waterproof membrane to be clogged extremely quickly when they enter each chamber in accordance with breathing phenomena of the box, which makes weatherproofing easily reduced. Also in the conventional type of apparatus, minimization thereof can not easily be realized.
The present invention was made for solving the problems described above, and it is an object of the present invention to provide a dehumidifying device in which humidity at a low level can be achieved in the side to be dehumidified (box side) and the stabilized and continued effect of the low humidity therein can also be achieved by water-vapor gas electrified by an electric apparatus accommodated in the box side, water-vapor gas existing in the outside air, or by any other floating dusts in the air which are easily electrified, or the like without the dehumidifying effect which is badly affected.